The present invention relates in general to a device for sensing the vibration of an object and, in particular, to a device which detects vibration by sensing disturbances in a fluid mass.
Various devices have been proposed which utilize a fluid mass for the purpose of detecting vibration of an associated object. For example, U.S. Pat. No. 1,082,014 to Digby et al discloses a vibration sensor which includes a receptacle containing a liquid, and a reflector element positioned in horizontal contact with but not submerged in the liquid. In this sensor, a beam of light is directed onto the upwardly facing surface of the reflector element, and a screen is positioned to receive the reflected beam. As the sensor is subject to vibration, the surface of the liquid will be disturbed, thus altering the angular orientation of the reflector element and varying the position of the reflected beam on the screen.
Another type of vibration sensor which utilizes a fluid mass is disclosed in U.S. Pat. No. 4,214,485 to Berger et al. In this patent, the sensor includes a light source adapted to transmit light through a container filled with a liquid, and a detector is mounted to receive light having passed through the surface of the liquid. As the container is vibrated, or the angular relationship of the surface of the liquid with respect to the incident light rays is varied, the light transmissive and refractive properties of the liquid surface are altered, thereby altering the output of the light detector.
A light transmitter and detector system has also been utilized in conjunction with a fluid mass for other applications. For example, U.S. Pat. No. 3,044,343 to Poitevin de Fontguyon discloses an optical instrument for use as a leveling device. In this device, a beam of light is directed onto and reflected from the surface of a container containing mercury. The tank can be fixed to an object to detect relative movement thereof. The light being reflected off the mercury can be utilized to level the object.